Mechanical manipulation of light or optical beams such as laser beams can be accomplished by a beam steering mirror through angular rotation or position translation of the mirror supported by a mirror mount. Some low cost manual mirror mounts for adjusting beam angles include a threaded screw pushing against a spring loaded plate holding the mirror, and, in operation, the screw can be turned manually to adjust for a precise mirror angle. Some low cost translation mirror mounts use a screw pushing against a spring loaded stage that can travel on bearings or slides, with the screw typically placed on the side of the mount.
In various designs, a motorized version of a mirror mount based on the above mentioned mounts uses a motor to drive the screw, or alternatively replaces the screw with a linear transducer for pushing the mirror plate. In implementations, the linear transducer can also be a piezoelectric device for achieving higher precisions but with a lower travel range.
In operation, mirror mounts can be adjusted in angle in a horizontal and a vertical direction, so as to redirect a beam precisely. FIG. 1 shows an example of a commercial mechanical mirror mount 100 that provides a mirror angle control via three adjuster screws to control the orientation of mirror holder with respect to a base plate.
A typical optical beam in various optical applications can be between a few millimeters to about a centimeter in diameter, and such a beam diameter allows a light beam in the visible or near infrared range to stay collimated over the distance of a laboratory table, e.g., a distance of several meters. The divergence angle due to diffraction is on the order of λ/D, where λ is the wavelength of the light and D is the beam diameter. For light in the range of 1 μm in wavelength and a beam diameter of 1 mm, the natural beam divergence will be approximately 1000 microradians based on this formula. In various applications, the mirror alignment resolution may be a fraction of this divergence, or in the range of 10's microradians. Many commercially available mirror mounts work in this range with various capability for adjustment and stability, depending on mount material and design, as well as actuator properties, such as use of fine pitch screws and differential micrometers for finer resolution.